Electromechanical devices such as starter, generator and so on have already been widely applied in many fields. There are numerous such electromechanical devices which have powerful functions, and these devices have played an immeasurable role particularly in such aspects of promoting social progress, improving people's life quality, etc. In general, an end cap structure (e.g., a front end cap, a rear end cap, and a drive end cap) is required to be equipped on these electromechanical devices and it will be connected with a housing of the electromechanical device. Existing end caps are typically made by means of mono-block casting. However, since the demands on the quantity of various electromechanical devices are huge and the specific applications are tremendously different, there are considerable differences in demands in terms of such aspects as contour dimensions, installing conditions, arrangements and so on during actual use. Existing various end cap structures, however, can neither adapt to and meet such differential demands, nor will they be advantageous for lowering costs in manufacture, installation and maintenance, thus causing considerable resources idling and wasting.